In order for a glazing unit to be positioned on and/or fastened to a structure, especially a motor vehicle body, it is in fact known to use at least one pin and preferably several pins, or one or more inserts, which are fastened beforehand to the glazing unit by partly embedding it or them in a plastic encapsulating material during what is called an encapsulation operation.
To carry out such an operation, the glazing unit and the insert or inserts are placed in a mold, in the desired relative position, and then a suitable plastic, for example polypropylene, is injected into the molding cavity of the mold so as to encapsulate a part of the insert or inserts on the glazing unit so as to fasten it or them to the latter.
Such inserts usually have three parts, namely a plane central part, or base, and, extending either side of said base, respectively a part that forms an active zone and is intended to cooperate with the body element and a part that is overmolded in the constituent material of the profiled sealing bead and includes a so-called pressure element, as explained below.
An insert may thus comprise a baseplate which is overmolded in said profiled seal portion and supports a base having a central axis and having a free face located outside said profiled seal portion, and also a pressure element which is firmly attached to the insert in at least one bonding region and extends between the baseplate and the pane, bearing on the latter.
During the encapsulation operation, the base, the baseplate and the pressure element of the insert are encapsulated in the encapsulation material and measures are taken to ensure that its active part is clear of this encapsulation material. To do so, the insert is placed in a mold so that its active part is isolated in a closed positioning cavity of said mold and so that its base and the part of the pane to be encapsulated are positioned in another cavity of the mold, called the molding cavity, into which the encapsulation material is injected.
A first difficulty extends from the fact that usually the glazing units for a vehicle, and in particular a motor vehicle, have complex shapes such that they require the use of specific inserts, the shape and size of the pressure element of which are dependent on the way they are positioned on the glazing unit. It may therefore be necessary, for one glazing model (i.e. a series of glazing units), to use several inserts having different shapes, thereby complicating the implementation of the overmolding operation insofar as each of the inserts has to be identified and positioned individually for each glazing unit.
A second difficulty stems from the fact that the sealing between the molding cavity and the isolated positioning cavity is not always perfect so that, during injection, it may happen that the injected substance tends to flow from the molding cavity into the positioning cavity, with the effect that the active part of the insert is partially encapsulated. As a consequence, subsequent problems in positioning said active part arise and/or difficulties in fastening it are encountered, so that the entire glazing unit runs the risk of being discarded as a defective component.
To alleviate this drawback, European patent application EP 0468713 proposes to place around the active positioning part, before the encapsulation operation, an elastomer seal which, when the insert is in position in the mold, is applied on the periphery of the positioning cavity so that it constitutes a seal between this cavity and the molding cavity, thus protecting the active part of the insert during the injection. Apart from the fact that such an arrangement is not always effective, it also has the drawback of complicating the manufacturing process.
International patent application WO 2008/145938 proposes to use an insert comprising a base placed on a baseplate of larger width, at the two ends of which two elastic lugs are respectively positioned which, during the overmolding operation, apply the base supporting the active part of the insert against the entrance of the positioning cavity by counter-reaction under the effect of the thrust of the pane.
Although in arrangements in which the pane is substantially parallel to the baseplate (or the base) the application force exerted by the lugs does have the effect of uniformly applying the base of the insert against the periphery of the entrance of the positioning cavity, this is no longer the case when the surface of the pane is inclined to the baseplate or to the base.